I propose to do a functional analysis of social behavior development in Gallus chicks. The objective of the first experiment is to determine what aspects of the natural context for filial behavior must be incorporated into a laboratory environment in order to obtain response patterns from chicks like those elicited by a broody hen in a social group. The social behavior of chicks obtained in laboratory imprinting studies has usually been unlike that observed in natural social groups. New evidence suggests that the use of inadequate parental objects and methods of object presentation account for the differences. Since most theoretical statements concerning the causation and development of social behavior in precocial birds have been derived from laboratory observations, it is essential that this matter be investigated. The approach taken will be to test chicks in laboratory situations which simulate key aspects of the natural context for filial behavior. The objective of the second experiment is to determine under what set of conditions it is possible to obtain stable social bonds between chicks and surrogate parental objects lasting beyond the sensitive period for the formation of mother-young attachments. Contrary to implications of previous reports, the presence of the imprinted phenotype on the second day after hatching, following exposures to a parental object on day one, does not necessarily demonstrate that stable social bonds have been formed; much evidence now suggests that responsiveness to novel objects has not diminished by the second day. Failures to demonstrate stable social bonds may be due to the use of inadequate parental objects. In this study, chicks will receive daily exposures to one of several parental models for five days after hatching and then be isolated for one week before being tested for social attachment. Use of this paradigm and appropriate control groups will ensure that any filial behavior exhibited is the result of social bond formation rather than an expression of continued sensitivity to novel parental objects. The proposed experiments are critical tests of the "neuronal model" and the "perceptual schema" hypotheses of perceptual development in chicks.